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Biomedical subjects

J C Riley

Publications and source records attributed to J C Riley.

At least 19 recordsLinked to original sources
PubMed2005

Milk fluoridation: a comparison of dental health in two school communities in England.

OBJECTIVE: To compare levels of caries experience in children attending schools in Wirral that have a fluoridated milk programme with children in a similar community which does not have a fluoridated milk programme. STUDY DESIGN: A cross sectional study measuring caries experience in first permanent molars. Children were examined on an 'intention to treat' basis and the effect of clustering of children within schools was taken into account. PARTICIPANTS: 690 children in Wirral (test group) and 1,835 children in Sefton (comparison group) were examined for caries experience (DMFT/DT/DFS) in 2003. The mean ages of the children examined in the test and comparison groups were 10.79 and 10.83 years respectively. RESULTS: Mean DMFT/DT/DFS values were 1.01/0.59/1.20 respectively in the test group and 1.46/1.02/1.89 respectively in the comparison group. Multiple linear regression analysis taking clustering of children within schools into account and with the Index of Multiple Deprivation 2000 as an explanatory variable gave the coefficients and p-values for DMFT/DT/DFS of 0.49 (p < 0.001)/0.43 (p < 0.001)/0.74 (p < 0.001) respectively. CONCLUSION: A difference in children with caries experience of 13% and a difference in children with active decay of 16% was found when a district with a community fluoridated milk programme was compared with a district without a fluoridated milk programme.

Animals↗
PubMed1999

The effect of water fluoridation and social inequalities on dental caries in 5-year-old children.

BACKGROUND: Many studies have shown that water fluoridation dramatically reduces dental caries, but the effect that water fluoridation has upon reducing dental health inequalities is less clear. The aim of this study is to describe the effect that water fluoridation has upon the association between material deprivation and dental caries experience in 5-year-old children. METHODS: It is an ecological descriptive study of dental caries experience using previously obtained data from the British Association for the Study of Community Dentistry's biennial surveys of 5-year-old children. This study examined the following data from seven fluoridated districts and seven comparable non-fluoridated districts in England: 1) dental caries experience using the dmft (decayed, missing, filled teeth) index; 2) the Townsend Deprivation Index of the electoral ward in which the child lived; 3) whether fluoride was present at an optimal concentration in the drinking water or not. RESULTS: A statistically significant interaction was observed between material deprivation (measured by the Townsend Deprivation Index) and water fluoridation (P < 0.001). This means that the social class gradient between material deprivation and dental caries experience is much flatter in fluoridated areas. CONCLUSION: Water fluoridation reduces dental caries experience more in materially deprived wards than in affluent wards and the introduction of water fluoridation would substantially reduce inequalities in dental health.

Child, Preschool↗
PubMed1999

Why sickness and death rates do not move parallel to one another over time.

Scholars sometimes claim that mortality and morbibity move papallel to one another over time. Using case studies from nineteenth-century England and Wales, this essay plots actual relationships in historical populations and explores why parallelism should not be expected. The implication of finding that mortality and morbidity chart independent courses is that they are either shaped by different factors or by the same factors operating in different ways. Hence morbidity should not be expected to be controlled by policies formulated to control mortality.

History, 19th Century↗
PubMed1996

The morbidity of medical practitioners.

In Volume 9, Number 1 of Social History of Medicine Robert Woods provides estimates for the mortality of Victorian doctors, showing that younger doctors and less well placed practitioners fared poorly. In part of that essay he attempts also to estimate the morbidity that doctors experienced, assuming a fixed relationship between mortality and morbidity risk. This comment explains why that assumption should not be made. Further, Woods relies on an objection Jacques Bertillon raised to infer that sickness time in Britain did not increase between the 1860s and the 1890s. This comment reviews the comparison that Bertillon made between British and continental friendly societies and explains the misunderstandings that nullify Bertillon's objection.

Europe↗
PubMed1993

Immunosuppressive levels of glucocorticoid block extrauterine luteolysins in the rat.

Leukocytes, normal constituents of the corpus luteum, release prostaglandins (PGs), superoxide, and hydrogen peroxide (H2O2) upon activation. These products appear to mediate luteolysis, and it has been postulated that activated leukocytes serve a role in corpus luteum regression. Glucocorticoids prevent leukocyte infiltration and activation by inhibiting cytokine production, secretion, and action, and also inhibit eicosanoid synthesis. The objective of the present studies was therefore to assess whether glucocorticoid would influence luteal regression in the rat. Ovulation and pseudopregnancy were synchronized in prepubertal rats by gonadotropin treatment. In uterine-intact rats, functional luteal regression, assessed from serum progesterone levels, began on Day 10 and was complete by Day 14. Dexamethasone blocked luteal regression in uterine-intact animals when administered daily from early in pseudopregnancy for as long as treatment was continued (up to Day 17). Immunosuppressive effects of dexamethasone were evident in the inhibition of estrogen-induced infiltration of eosinophils, as shown by abrogation of estrogen-induced uterine peroxidase activity, and high continuous levels of dexamethasone were necessary to block luteolysis. Hysterectomy extended luteal function by several days, with maintenance of maximal serum progesterone levels up to Day 12; but serum progesterone levels were reduced about 50% by Day 16 and completely depressed by Day 19. Dexamethasone treatment of hysterectomized rats from Day 12 until Day 15 or 18 blocked the decline in serum progesterone levels. Dexamethasone treatment did not block the decrease in serum progesterone levels induced within 24 h by PGF2 alpha in uterine-intact animals on Day 9 or in hysterectomized animals on Day 19.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

In vivo generation of hydrogen peroxide in the rat corpus luteum during luteolysis.

The hypothesis that hydrogen peroxide generation occurs in the corpora lutea of superovulated rats during luteolysis was tested using a peroxide-dependent inhibitor of catalase, 3-amino-1,2,4-triazole (AT). Luteal regression was induced during midpseudopregnancy by injection of 500 micrograms prostaglandin F2 alpha (PGF2 alpha) 1 h before administration of AT (0.1 g/kg, ip) and was confirmed by progesterone analysis of peripheral blood serum. Within groups of both PGF2 alpha-treated and untreated control rats, other rats also received ethanol (0.2 g/kg, ip), which prevents hydrogen peroxide-mediated inhibition of catalase by AT. Diluted homogenates of ovaries removed 1 h after AT administration were assayed for catalase activity by measuring the decrease in absorbance at 240 nm for 30 sec after the addition of hydrogen peroxide (10 mM). Ethanol-sensitive catalase inhibition by AT was significantly higher (47.9 +/- 3.38%) in samples from PGF2 alpha-treated groups than in controls (23.1 +/- 4.82%; P less than 0.01; n = 9). Similar increases in catalase inhibition by AT were found in luteal tissue of rats treated with PGF2 alpha 24 h earlier and in rats in which luteolysis was allowed to occur spontaneously in late pseudopregnancy. Hemoglobin an AT assays revealed that the changes in catalase activity were not the result of altered blood contamination or AT concentration in the luteal homogenates. Since catalase inhibition by AT is only seen in the presence of hydrogen peroxide, these results support the conclusion that an early and sustained component of corpus luteum regression is the generation of hydrogen peroxide in luteal tissue.

Amitrole↗
PubMed1991

Oxygen radicals and reactive oxygen species in reproduction.

Free radicals and reactive oxygen species play a number of significant and diverse roles in reproductive biology. In common with other biological systems, mechanisms have evolved to minimize the damaging effects that these highly reactive molecules can have on reproductive integrity. Conversely, however, recent findings illustrate the constructive roles that oxygen radicals and reactive oxygen species play in a number of important junctures in the development of germ cells and the obligate endocrine support they receive for the successful propagation of the species. Specifically addressed in this review are some aspects of sperm development and action, the uterine environment, oocyte maturation and ovulation, and corpus luteum function and regression.

Animals↗
PubMed1989

Plasma membrane changes during corpus luteum regression.

Structural and biochemical changes were examined in the plasma membrane of luteal cells during corpus luteum regression. Structural alterations as indicated by an increase in the liquid-crystalline to gel phase transition temperature and a decrease in plasma membrane fluidity were observed during luteolysis in microsomes and in plasma membranes prepared from prostaglandin F2 alpha-treated rats, when samples were examined by wide angle x-ray diffraction and fluorescence polarization. In addition, a significant increase in activity of the lipolytic enzyme phospholipase A2 appeared during incubation of plasma membrane samples and dispersed luteal cells at 40 degrees C in the presence of 1.0 mM CaCl2. Similar incubation conditions also produced a drop in human chorionic gonadotropin (hCG) binding in luteal samples from prostaglandin F2 alpha-treated rats. These results indicate that during luteolysis there are important structural changes in the plasmalemma of regressing luteal cells. These alterations appear related to an increase in phospholipase A2 activity and a decrease in hCG receptors. These modifications may account for the decrease in function during corpus luteum regression.

Animals↗
PubMed1989

The effects of prolactin and prostaglandin F2 alpha on plasma membrane changes during luteolysis in the rat.

The ability of PRL to modify prostaglandin F2 alpha (PGF2 alpha)-induced membrane changes during functional corpus luteum regression was examined in the pseudopregnant rat. Fluorescence polarization studies conducted 24 h after sc injection of PGF2 alpha revealed a marked and significant increase in the polarization parameter, which is suggestive of reduced plasma membrane fluidity. At the same time, there was a decrease in hCG binding and a significant increase in apparent phospholipase-A2 activity during incubation of dispersed rat luteal cells. Each of these changes was attenuated when the animals were pretreated with PRL 30 min before PGF2 alpha. The decrease in plasma progesterone caused by PGF2 alpha treatment was also inhibited by PRL. PGF2 alpha also stimulated a significant polarization increase in dispersed cells prepared from ovaries removed 1 h after injection of this luteolytic agent, although this effect could not be demonstrated in plasma membrane samples. These results indicate that PRL and PGF2 alpha affect the same membrane pathway in the rat corpus luteum and that this pathway appears to be closely coupled to luteal cell function.

Animals↗
PubMed1988

Impairment of gonadotropin binding occurs during membrane rigidification in plasma membrane samples prepared from regressed rat corpora lutea.

The effect upon human chorionic gonadotropin (hCG) binding of a 90-min incubation of plasma membranes prepared from the corpora lutea of control and prostaglandin F2 alpha injected rats was studied. After incubation for 90 min with 1 mM CaCl2 at 40 degrees C, single point hCG binding assays at room temperature revealed a significant decrease in the degree of binding of approximately 50% in membrane samples prepared from regressed corpora lutea. The binding decrease in regressed samples did not occur if the incubation temperature was reduced to 35 degrees C or if calcium ion was replaced with magnesium. Scatchard analyses indicated that the decrease in binding capacity was the result of a loss of gonadotropin receptors rather than an affinity shift. Specific activities of two membrane-bound enzymes (Na+-K+ ATPase, 5'-nucleotidase) did not change in a correlative fashion during the incubation. In previous studies the same in vitro conditions caused a substantial and significant decrease in membrane fluidity, as determined by fluorescence polarization. Thus it appears that the membrane rigidification is of a specific nature and interferes with gonadotropin binding during luteolysis.

Animals↗
PubMed1987

Involvement of phospholipase A activity in the plasma membrane of the rat corpus luteum during luteolysis.

Plasma membrane samples prepared from corpora lutea (CL) of control and prostaglandin F2 alpha-treated rats were incubated with radiolabeled phosphatidylcholine for 90 min at 40 C with 1 mM CaCl2 to test for the presence of phospholipase A2 activity. At the end of the incubation period, labeled arachidonic acid cleaved from the 2 position of the phospholipid moiety had accumulated to 10.7 +/- 2.4% (mean +/- SE) of the initially added radioactivity in the prostaglandin F2 alpha-treated samples, with 3.7 +/- 1.2% appearing in the controls. Arachidonic acid production was inhibited by calcium chelation and by the phospholipase A2 inhibitor bromophenacyl bromide, indicating heightened activity of phospholipase A2 in CL plasma membranes undergoing regression. Unexpectedly, radiolabeled lysophosphatidylcholine was produced in regressed membrane samples at a similar rate, suggesting the induction of phospholipase A1 activity as well. To determine if the membrane rigidification that occurs with regressed membrane samples under the same incubation conditions is caused by the hydrolysis products of phospholipase activity, fluorescence polarization experiments with the probe trans-parinaric acid were conducted. Washing of incubated membrane samples with fatty acid-free BSA, which selectively removes free fatty acids and lysophosphatides from the bilayer, resulted in a restoration of the fluidity to levels recorded at the onset of the incubation. These results suggest that the previously described decreases in CL plasma membrane fluidity and hCG binding in vitro during luteolysis are caused by a synergistic effect of calcium ion and hydrolysis products of phospholipase A activity.

Animals↗